NXT PROGRAMMING Bill Johnson

Agenda:

- Intro (ASU BEST video)

- Resources (AZFLL.com)

- Workshop (learning the basics)

- FLL Team Prep (stages)

- Wrap up

azfll.com

• “Starter Documents”

– FREE NXT Training Course

– 2013 Arizona FLL Introductory Coach/Mentor

Workshop: 2013 Arizona Coaches

Workshop Introduction/Intermediate –

Recording includes veteran coach advice

- NXT Programs – Robot Building Instructions

– STEMcentric NXT Robotics Tutorial

– STEMcentric EV3 Robotics Tutorial *NEW*

Resources II

– NXT Curriculum (PDF)

– 5 Minute Bot Assembly Instructions (PDF)

– Wheelie Assembly Instructions (PDF)

– Turning Jig Assembly Instructions (PDF)

– Robot Challenge Worksheet (PDF)

– Programming Examples (PDF)

– Intermediate Robotics Presentation (PowerPoint - PDF)

– LEGO MINDSTORMS Sensor Programming (PDF)

• Show video

Bot Basics (ASU Best Video)

• Bot build

• X-Y movement (distance/turns)

• Simple sensors (light/ultrasonic)

• Line following

• “Mission mapping”

Session I

• Overview the pre-built bot

• Overview the Mindstorms software

• Workshop methodology

5 Min Bot Sound sensor

Ultrasonic

sensor

NXT Controller – The Brick Motor Ports (A, B, C)

Power On and Select

Select Buttons

Back Button or Program Cancel

Icons representing menu options

Sensor Ports (1, 2, 3, 4)

USB Port

Section 1: Software Overview and

Building

Mindstorms Software Overview

• Fire up Mindstorms software

• Type in “First Program” and hit “GO>>”

• Expand workspace (click red cross upper

right corner)

Configuration Panel NXT Brick Status

Download Program

Tool Panel Select

Light Green – Robot Actions

Yellow – Read Sensors

Orange – Program Flow

Dark Orange – Math/Data

Dark Red - Advanced

Dark Green – Common Commands

Program Map Window

Program Flow

Not in Program Flow

Motors that

will be given

the

command.

Duration –

Is it

rotations,

degrees,

time, or

unlimited? Power Level

Motor

Direction

Move Block Configuration Panel

Section 1: Software Overview and

Building

Toolbar Icons

New File/Open Program/Save Program/Cut/Copy/Paste/

Undo/Redo/Pointer/Pan Tool/Comment Tool/MY Blocks

Pull Down Menus (File - open/save/print/etc.; Edit; Tools; Help)

NXT Brick Status

Download Program

Program Map Window

Generate A Simple Program

Forward/Backward Loop 4 times

Forward/turn

Play a sound

Workshop Methodology

Three hands-on sessions – in each session:

– brief instructions (how to’s)

– tasks/challenges will be presented

– hands-on activities

– discussion of observations/learning

Operations:

– work in teams of 2-3

– note observations/list questions

– ask mentors for help

– stop working and listen during instructional times

• Show Boys/Girls Club video

Obstacle Race Challenge

(strategies/mission mapping)

First Robot Across Finish Line WINS!!

Step Meas. Control

1 F 16” 2.3

2 R 45° 0.48

3 F 8.5” 1.2

4 R 90° 0.96

5 F 30” 4.3

1 1

2

4

3

5

Problem Solving Process

• Develop strategy (pick a path)

• Map path (measure distances/angles)

• Convert physical measurements to computer

control parameters

• Generate program & download to robot

• Test

• Adjust parameters/program as needed

Problem Breakdown (what’s needed to be done)

• How do you move the bot a specified

distance?

• How do you make the bot turn?

• How do you convert physical

measurements to control parameters?

(bot calibrations – distance and turns)

Tasks/Challenges

• Calibrations

– tire circumference

– turn angles

• Challenges

– parking (without and with turn)

– “closest to wall” (without and with turn)

– “design your own”

• Extensions (different speeds, backwards, use your imagination)

Tattletale to help

count rotations.

Tool to visualize wheel operation

(distance traveled vs tire circumference)

Move Calibrations

Math Learning:

distance vs wheel geometry, data plotting,

formulas

Issues:

measurement skills, math (fractions, etc.),

documentation

Linear Moves

distance traveled, Dt = n × C where n = number of tire rotations, C = tire circumference

Calibration Task 1: accurately measure

tire circumference

C = Dt / n

Note: Dt = S × t where S = speed, t = time is NOT

recommended (speed is not constant)

Bot Distance Calibration

Challenge 1: Moving into Parking Space

Starting Line Finish Lines

Start anywhere behind the starting line and stop the NXT in between

the finish lines. The NXT must not be over any line.

The NXT must be

completely within

lines.

Challenge 2: Closest to the Wall

Starting Line Wall

Start the NXT any where behind the starting line. The NXT should move forward

and come within 1 centimeter without any piece of the NXT touching the wall.

The NXT should

stop within 1 cm

of the wall.

Please stop

working and be

ready to

discuss.

Session II - Turning

• Types:

– one wheel (pivot turn)

• forward

• reverse

– tank turn (one wheel backwards, one

forward)

– two wheel (different wheel speeds)

•

Tire Rotations

Visualizing Turn Mechanics

Turning Jig

One wheel turns while the

other is locked into position.

Tire rotations = path length/tire circumference

# rotations = ( desired angle/360°)( 2πr ) / C

r => turning radius (distance between the tires – center to center)

C => tire circumference

Predictable Turn Angles

r

Turn Calibration Exercises

• 360° Turns calibration (This will serve as a basis for other turn parameters)

• Four turn test (This test highlights errors over multiple movements.

Errors compound, so minor parameters errors will

create large inaccuracies in final placement.

Issues:

right vs left turns, weight distribution,

sliders vs castor wheel, etc.

Turn Calibration (360°Test)

Program three MOVE blocks:

forward 2 rot/one wheel turn (~ 6 rot)/forward 1 rot

Perfect Turn Parameter

Oversteer (decrease turn)

Understeer (increase turn)

Four Turn Test

Program: place two MOVE blocks into a LOOP block

Under steer

Over steer

Terminology Issue:

Turn angle degrees vs

wheel rotation degrees

Challenge 3: Turn to Park

Starting Line

Parking Space

Start the NXT any where behind the starting line. The NXT should move forward

and turn to park within the parking space. No part of the NXT can be touching or

over the boundaries.

No part of the NXT can be out of

the parking space.

Challenge 4: Turn to Closest to Wall

Starting Line

Wall

Start the NXT any where behind the starting line. The NXT should move forward,

turn towards the wall, park between the lines, and stop within 1 centimeter of the

wall. No part of the NXT can be touching the wall.

Distance should

be less than 1 cm.

Please stop

working and be

ready to

discuss.

Discussion Points

Linear/turn moves

– How does the initial placement affect the ending

position?

– How can you accurately place the robot in the

beginning?

– Does wheel size affect turn parameters?

– castor wheels and sliders – which is better?

– How do surfaces effect turn accuracy?

– Does weight placement affect the turn? Where

should the weight be placed on a robot?

Session III – Using Sensors

Sensors allow the robot to gather information to

find intermediate reference points or landmarks.

Shorter move distances = Less error

Dynamic information gathering = Larger margin of error

Guiding Question: How might we use sensors to find reference points to move the robot more accurately, consistently, and predictably?

Section 3: Using Sensors

Section 3: Using Sensors

Section 3: Using Sensors

Section 3: Using Sensors

Session III – Using Sensors

(How might I move the robot more accurately,

consistently, and predictably?)

Touch

Color Light

Sound Ultrasonic

Rotation Section 3: Using Sensors

Basic Sensor Program (WAIT Block)

Use common blocks

MO

VE

un

lim

ited

WA

IT u

nti

l tr

igg

er

ST

OP

Do NOT use Sensor from

“Senor Read Menu”

WAIT Block

• WAIT Block Operation:

keep doing whatever action that is being done BEFORE the WAIT block, UNTIL the desired sensor is triggered – then continue actions along the sequence beam

examples: – stopped - sensor trigger - move

– moving forward “unlimited”- sensor trigger - stop

– etc.

Light

Rotation

Ultrasonic

Color

Touch

Move Block Configuration Panel

Section 3: Using Sensors

Sensor Exercises

• ultrasonic wall sensing

• line sensing (need light calibration)

• sensor combinations

• line following

Please stop

working and be

ready to

discuss.

Stages for FLL Team Prep

• Learn the basics 3-6 wks

• Generate initial game strategies/missions

START SIMPLE! 2-4 wks

• GO TO A SCRIMMAGE (mid to end Oct)

• Reassess strategies/missions 2-4 wks

• Use last 1-2 wks to practice “final missions”

Wrap Up

• Robotics is educational AND FUN!!!

• Coaches should always be assessing

their team’s capabilities and adjust

their program as needed

• There are a multitude of learning

opportunities – less instruction leads to

more learning